CORE B (Biostatistics) The Biostatistics Core (Core B) seeks to assure that all CRC investigators have access to state-of-the-art biostatistical support for all aspects of the design and conduct of their investigations. Specific Aim 1: To provide collaborative statistical support for investigations conducted by the members of the CLL Research Consortium (CRC) 1.1 To provide statistical support for the clinical research studies conducted by the CRC. 1.2 To provide statistical support for the laboratory studies conducted by the CRC, including both freestanding studies within the Projects and laboratory correlative studies embedded in the clinical trials. 1.3 To provide statistical support for murine studies conducted by the Projects. Specific Aim 2: To participate in the quality assurance and quality improvement processes for the CRC database 2.1 To participate in an ongoing process of quality improvement for the CRC database. 2.2 To advise on quality assurance as new types of data are incorporated into the CRC database. Specific Aim 3; To participate in the scientific advisory committees of the CRC 3.1 To participate in teleconferences and meetings held by the Clinical Advisory Committee, the Scientific Advisory Committee, and the Data Safety and Monitoring Board. 3.2 To participate in the review of all sample requests submitted to the Tissue Core (Core C). Specific Aim 4: To provide a forum for statisticians working in CLL 4.1 To provide, through the distributed Biostatistics Core, a forum for statisticians working in CLL to improve their understanding of the disease and thereby provide even better statistical support to the Projects.